1. Field of the Invention
The invention relates generally to the field of oil and gas well wireline operations. More specifically, the present invention relates to a method and apparatus to enhance the ability of wireline operations in deep water wells.
2. Description of Related Art
Many wireline procedures exist today for use in hydrocarbon producing well bores. These procedures include, well logging, well perforating, and plug setting. Often times wireline procedures are performed after the well has been completed and thus the well drilling equipment has been removed from the well. While this is not a problem regarding hydrocarbon producing well bores that are located on the earth""s surface, wells that are located on the sea floor can be problematic, especially wells that are in ultra-deep waters (from about 1000 feet in depth in excess of 10,000 feet in depth). While a drilling rig can be used in wireline operations for sub-sea wells moving an off shore drilling rig back to a well site specifically for wireline operations after the well has already been drilled is very expensive. Because of the expense of owning and operating offshore drilling rigs, once the offshore drilling rig has completed drilling a well, the rig is generally relocated to the next drilling site. Because wireline operations are often performed to maintain sub-sea wells in their optimum producing capabilities, and because wireline operations generally occur well after the wells have been drilled and the offshore drilling rig has been moved to another location, a method and apparatus is needed that enables the use of wireline operations (including coiled or conductor tubing) on sub-sea hydrocarbon producing wells, without requiring the use of an offshore drilling rig.
The present invention involves a remote sub sea lubricator assembly for inserting a wireline tool into a well through a sub sea well head. The remote sub sea lubricator assembly comprises an elongated tube having an axial passage formed therethrough for receiving the wireline tool. The elongated tube preferably has a circular cross section, and is typically approximately 20 feet in length. However, because the elongated tube must accommodate the specific wireline tool, the length of the elongated tube can exceed 100 feet. As far as the inner diameter of the elongated tube, while that value can vary, it must be of sufficient diameter to enable free passage of the wireline tool therethrough. The elongated tube has a top end, a bottom end, an inside and an outside and the wireline tool is attached to a wireline. The sub sea well head is connected to a well bore at the sea floor.
The top end of the remote sub sea lubricator provides an aperture for receiving the wireline and has a sealing means for producing a sealing contact between the aperture and the wireline passed therethrough. The sealing means prevents pressure communication across the aperture while allowing free passage of the wireline through the aperture. The top end of the remote sub sea lubricator is detachable, and preferably threadingly attached to the elongated tube, although the top end can be attached to the rest of the remote sub sea lubricator can also be attached with flanged or bolted fittings. The bottom end of the remote sub sea lubricator is formed to coaxially mate with the sub sea well head, this provides pressure communication between the axial passage of the elongated tube and the well bore.
The wireline tool is releasably secured to the inside of the remote sub sea lubricator, where the securing means can be actuated to obstruct free passage of the wireline tool through the elongated tube and alternatively can be actuated to allow free passage of the wireline tool through the elongated tube. The securing means can be comprised of a full port ball valve, a ball valve, a gate valve, a flapper, or any other suitable means capable of capturing the wireline tool inside of the elongated tube and releasing it as well.
The remote sub sea lubricator further comprises a locking mechanism for securing the remote sub sea lubricator to the sub sea well head. Many types of locking mechanisms can be employed to secure the remote sub sea lubricator to the well head, one type involves a plurality of recesses formed on the outer radial surface of the bottom of the elongated tube formed to receive similarly shaped knobs located on the inner radius of the well head opening.
The remote sub sea lubricator also comprises a means for sealing between its bottom end and the sub sea well head to prevent pressure communication across the region where the outside of the elongated tube contacts the inside of the sub sea well head. The sealing means here will include one or more elastic seals that circumferentially traverse the outer diameter of the bottom end of the elongated tube. The seal dimensions will depend on the dimensions of the bottom end and of the sub sea well head. The seal materials will depend on the environment in which the seals are to be used.
The top end of the remote sub sea lubricator can include a compressible pack off rubber having a coaxially situated axial passage therein formed for passage of a data transmitting wireline therethrough. The top end also includes a pack off bushing and a piston. The piston has a high pressure supply side and an ambient pressure side, where the ambient pressure side is in pressure communication with the inside of the elongated tube. The piston and the pack off bushing both should have a higher modulus of elasticity. The pack off rubber is located between the pack off bushing and the piston. When the high pressure supply side exceeds the ambient pressure side the resulting pressure difference urges the piston toward the pack off bushing which then compresses the pack off rubber between the piston and the pack off bushing. Compression of the pack off rubber causes the axial passage within the pack off rubber to sealingly encase the wireline which then prevents pressure communication through the axial passage.
The present invention also includes a pressurized canister that is in pressure communication with the high pressure supply. Generally, the pressurized canister is pressurized to a pressure of from 200 pounds per square inch to 400 pounds per square inch above the pressure of the well bore. Alternatively, the high pressure supply may be comprised of sub sea hydrostatic pressure. The pressurized canister provides a pressure source to the high pressure side of the piston, where the pressure source can be regulated.
A method of using the remote sub sea lubricator involves inserting a wireline tool into a sub sea well bore comprising the steps of inserting the wireline tool into an elongated tube and securing the wireline tool within the elongated tube. Then the wireline is threaded through the top of the elongated tub, or alternatively a pressure pack off head, and the wireline is connected to the wireline tool. The top of the elongated tube is then attached to the remaining sections of the remote sub sea lubricator. The connection can either be threaded, welded, or flanged.
After the wireline tool is secured within the elongated tube, the elongated tube containing the wireline tool is lowered adjacent to the sub sea well bore. The bottom of the elongated tube is then inserted into the sub sea well head and the elongated tube is secured to the sub sea well head. The wireline tool is then released from the inside of the elongated tube by deactivating the securing means. This allows the wireline tool to be lowered into the sub sea well and for wireline operations to commence. The wireline operations can include well logging, perforating, or other mechanical services as are well known in the art.
Once wireline operations are completed, the wireline tool is raised from inside of the sub sea well back into the elongated tube. The wireline tool is resecured within the elongated tube and the elongated tube is disconnected from the sub sea well. The elongated tube containing the wireline tool is raised up and away from the sub sea well.